Assessing and mitigating risks to bridges from large wood using satellite imagery

The transport and accumulation of floating large wood (LW) debris at bridges can pose a major risk to their structural integrity. The impact forces arising from collisions of LW can cause significant damage to piers, and accumulations can constrict the flow and exacerbate scour at piers and abutments. Furthermore, LW accumulations increase afflux upstream of bridges, heightening flood risk for adjoining areas. Consequently, there is a need for a practical and rapid approach to identify bridges prone to LW-related hazards and to prevent the formation of LW accumulations. This paper proposes an approach based on satellite imagery to (i) quantify the risk of LW at a bridge structure and (ii) locate a LW-trapping system upstream of the identified vulnerable bridges to dramatically reduce risks of LW-related damage. This methodology is applied to major rivers in Devon (UK). 26 bridges were identified as at risk to LW with the majority prone to LW jams. Furthermore, satellite imagery was used to identify 12 locations for the potential installation of LW trapping systems for bridge protection. The results reported in this paper show that satellite imagery is a powerful tool for the rapid assessment and plan of mitigation measures for bridges at risk to LW.